Method of cleaning a drop separator and drop separator with cleaning device

ABSTRACT

A method for cleaning a drop separator includes the steps of mounting a plurality of parallel blades along a gas channel, spraying the blades with cleaning jets of wash water pulsed from a plurality of flat jet nozzles, and displacing the plurality of the nozzles perpendicular to a direction of gas flow while spraying the blades.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase application corresponding toPCTEP91/02348 filed Dec. 7, 1991 and based in turn, upon an applicationfiled in Germany as P 40 41 165.6 filed Dec. 21, 1990 under theInternational Convention.

FIELD OF THE INVENTION

This invention relates to a method for cleaning a drop separator and toa cleaning device carrying out the method.

Downstream of any gas scrubber generally a drop separator is provided ina first scrubber of a two-stage gas scrubbing installation, e.g. for thecleaning of flue gas, with a first scrubber for the removal of dust andoptionally of HCl and a second scrubber for SO₂ removal.

A drop separator has plates, called separator plates or blades extendingover the entire cross section of a gas channel, e.g. a flue gas channeland which are arranged parallelly to each other and curved in the flowdirection of the flue gas. The arrangement of the blades is known forinstance from "Perry's Chemical Engineering Handbook, Sixth Edition,FIGS. 18-110 (b)", or from the publication "HochwirksameTropfenabscheider bei der Rauchgasreinigung (Sonderdruck aus Heft 1/83Chemische Industrie)". The drops contained in the gas or separated atthe blades run down on the blades acting as baffle surfaces. The problemwith such drop separators are the deposits forming on the blades, whichtend to clog the drop separator.

In order to clean the drop separator it is known from theabove-mentioned publication to provide the drop separator with acleaning device equipped with stationary nozzles installed in the gaschannel. The nozzles arranged before and optionally also after theblades in the flow direction of the gas are fully conical nozzles, whosecone covers the entire cross section of the gas channel (compare withFIG. 4). The cleaning during which the blades are sprayed and rinsedwith cleaning water jets corresponding to the conical shape of thenozzle takes place at intervals.

Particularly in the case of flue gases with a high proportion of flyash, such as, for instance, downstream from an older electrofilter, thecleaning performed by this nozzle arrangement is not satisfactory. Thedrop separator clogs easily which results in frequent standstills, whilethe deposits are removed, for instance, by water under high pressure orby compressed air. In the worst cases the drop separator has to bereplaced.

An essential drawback of the cleaning methods using stationary conicalnozzles consists in the fact that the separator plates are not evenlyhit by the cleaning jets. Blind spots are formed from which the cloggingof the drop separator starts.

OBJECTS OF THE INVENTION

It is the object of the invention to develop a method for cleaning adrop separator which obtains an improved cleaning efficiency. The otherobject of the invention is to provide a drop separator capable ofcarrying out the method according to the invention.

SUMMARY OF THE INVENTION

According to the method of the invention the mutually parallel blades,curved in the direction of the gas flow are cleaned by moving flatcleaning jets over the blades transversely to the longitudinal extent ofthe blades.

The blades are swept by the cleaning jets with the same force and at thesame angle. In opposition thereto the force of a conical, stationary jetdecreases from the center of the jet outwardly. As a result the variousblades hit by one jet are swept with variable force and at variableangles, which leads to the already mentioned blind spots. Therefore animportant advantage of the method is the fact that the blind spots, i.e.areas which are hit by the cleaning jets only slightly or not at all,can be avoided to the largest extent.

Besides, fewer nozzles are required. Also the water amount required pernozzle is lower when compared to the water amount required by thecleaning with stationary, conical cleaning jets.

A further advantage of the method is the use of cleaning jets ejected byflat nozzles, whose force--and therefore their cleaning effect --isessentially bigger than the one of conical cleaning jets. Besides whenusing flat cleaning jets it is possible to set the angle of the oncomingflow with respect to the blade arrangement so that the areas of theblades mostly exposed to contamination can be reached as extensively aspossible.

The moving of cleaning jets leads to a uniform, mechanically enhancedcleaning of the blades and as a result to a longer life of the dropseparator.

The advantage of the method is a stronger cleaning process.

According to the method the blades are set to vibrate, which leads to afurther increase in the efficiency of the cleaning process.

Another advantage of the method is the cleaning process which isenhanced by the use of an abrasive substance, such as sand, in thewater.

The cleaning process is also enhanced according to the invention bydissolving the deposits with the aid of an additive, e.g. sulfuric acid,in the wash water.

The apparatus according to the invention includes the nozzle pipesmounted on a frame which is movable in the gas channel essentiallyperpendicular to the longitudinal extent of the blades and perpendicularto the direction of gas flow, thus displacing the cleaning jets over theblades during an interval with the aid of a simple linear drive.

Flexible hoses compensate for the motion-conditioned variations in thedistance of the nozzle pipes to the wash water supply.

The flat jet nozzles which are arranged so that perpendicularly to theblades a flat jet is formed while parallelly to the blades a fan-likejet is formed, generate a highly mechanical cleaning effect.

According to the invention the frame of the cleaning device is connectedby swinging bars to a fastening device, e.g. carrier, in the gas channelor with a channel cover. The advantage of the mobility of the frame dueto a swinging arrangement is that the frame remains mobile when it hasbeen contaminated by dirt. This feature is particularly suitable fordrop separator with horizontal flow.

According to a further feature of the invention the frame of thecleaning device is connected with a chassis. To make the displaceabilityof the frame possible by means of a chassis is a simple solution and canbe particularly suitable for a drop separator with vertical flow.

Still according to a further feature the simple connection between theframe and the linear drive is utilized.

The simple connection of the hoses with the wash water supply is alsosuggested.

Advantageously several nozzle pipes are supplied by a single hose. Thisfeature is particularly suited for gas channels with small crosssection.

The mouth pieces according to the invention prevent the fan-likedispersion of the cleaning jets by the gas flow. This leads to anenhanced cleaning. It is particularly effective to arrange the mouthpieces behind the blades in the direction of the gas flow and thereforesuitable for a drop separator with nozzles arranged behind the blades,because the jets have to hit the blade surface against the direction ofthe gas flow.

A further positive effect of the mouth pieces consists in the fact thatthe areas of the drop separator impacted by the cleaning jets arecovered by the mouth pieces, so that in these areas the drop separatoris not traversed by the gas stream partially entraining the drops.

The cleaning process can be further improved by an adjustable impactangle of the flat jet nozzles, according to one of the features of theinvention.

Finally the apparatus is designed to prevent the washing fluid fromescaping of the end of a cleaning interval.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become morereadily apparent from the following description, reference being made tothe accompanying drawing in which:

FIG. 1 is a side view of the cleaning device of the drop separator withhorizontal flow;

FIG. 2 is a partial vertical section of the drop separator with cleaningdevice; and

FIG. 3 is a part of a horizontal section;

FIG. 4 is another embodiment of the cleaning device;

FIG. 5 is a drop separator with vertical flow and provided with thecleaning device according to the invention; and

FIG. 6 is another embodiment of the drop separator with vertical flowaccording to the present invention.

SPECIFIC DESCRIPTION

A drop separator with horizontal flow, as shown in FIG. 1 is arranged inthe flue gas channel between a first and a second scrubber of a gasscrubbing installation, has a four-tier separating device covering thecross section of the gas channel, whereby in each tier five bladepackets 1 are arranged next to each other. The blade packets 1 aresupported on carriers 2 arranged between the blade packets 1 and runningperpendicularly downward, through all tiers. Underneath the bladepackets 1, there are water collecting tanks 3 and in their middleprofiles 4, whereby the water collecting tanks 3 abut the profiles 4 ofthe blade packets 1 arranged therebelow.

The drop separator has a total of twenty blade packets 1. The surfacescovered by the carriers 2, the water collecting tanks 3 and the profiles4, as well as the borders of the separating installation are shielded infront and behind the separating installation, in the direction of thegas flow.

In the blade packets 1, blades 5 having a contour curved in thedirection of the flue gas flow (arrow A in FIG. 3) with a so-calleddrain nose on the apex of their curvature, are arranged parallelly toeach other. The blades 5 of the two halves of a blade packet 1 dividedby the profile 4 are mirror images of each other and readily seen inFIG. 3.

A cleaning device of the drop separator has a frame on each front andrear sides of the separating installation, in the direction of the fluegas.

Each of the frames has a middle section 6 with respective five carriersections 7 fastened thereto and running in upward and downwarddirections. In order to reinforce the stability of the frame, thecarrier sections 7 are connected to each other and to the middle section6 by bracing sections 8. In this case the bracing sections 8 form anupper and lower "V".

The frame is mounted by means of two swinging bars 9 to a cover of theflue gas channel. The swinging bars 9 are connected via links 10 withthe middle section 6 and via further links 11 with the cover of the fluegas channel. This way the frame is movably mounted in the flue gaschannel.

The middle section 6 is connected with a drive rod 12. The drive rod 12leads via the packing box 13 through the wall of the flue gas channeland is connected to a linear drive, e.g. a spindle drive. The drive canbe of the electric, hydraulic or pneumatic kind.

On the carrier sections 7, in each tier three mutually parallel nozzlepipes 14 are arranged, which run perpendicularly with respect to theblades 5. Symmetrically on both sides of a carrier section 7, on anozzle pipe 14 there is a nozzle arrangement with three flat jet nozzles15, mounted on extension arms 16 extending upward and downward from thenozzle pipe 14 and on the nozzle pipe 14 (FIG. 2). This way on a nozzlepipe 14 there are thirty flat jet nozzles 15.

The cleaning device is arranged in front of the separating installationso that the carrier sections 7 run vertically over the middle of theblade packet 1. The distance between the nozzle arrangements on bothsides of a carrier section 7 of a nozzle pipe 14 is slightly less thanhalf the width of a blade packet 1. The distance between the flat jetnozzles 15 of a nozzle pipe arrangement, the distance between the lowerflat jet nozzles 15 of an upper pipe nozzle 14 and the distance of theupper flat jet nozzles 15 of a nozzle pipe 14 lying underneath it in thesame tier is the same.

The flat jet nozzles 15 are designed so that the impact angle of thecleaning jets can be adjusted between 0° and 15°. An angle of 10° isset. Thereby the directions of the jets of the flat jet nozzles 15 ofthe two halves of a blade packet 1 are spread apart in a symmetricalmirror image of each other, so that the cleaning jets are aimed betweenthe curved blades 5 (FIG. 3).

In this example, each time two nozzle pipes 14 are connected to eachother via connection pipes 17. To this total of six connection pipes 17the hoses 18 are connected. These hoses are connected to a connectionsocket 19 provided in the wall of the flue gas channel. Outside, infront of the wall there is a supply pipe 20 for the wash water, whichbranches into the connection socket 19 over solenoid valves 21.

In a variant of the drop separator, mouth pieces 22 are provided, whichare shaped like flat funnels and start from the flat jet nozzles 15extending towards the blades 5. Preferably these mouth pieces 22 aremounted only in the flow direction of the flue gas downstream of theseparating installation. A mouth piece 22 for a flat jet nozzle 15 hasbeen drawn in FIG. 3 as an example.

In a further variant, each of the two frames are connected with achassis, having two wheels 23 and two mountings 24. The mountings 24 arefastened to the walls of the flue gas channel and are provided withrunning surfaces for the wheels. The wheels 23 are each fastened underthe middle sections 6 on their ends (FIG. 4).

In a further variant, all flat jet nozzles 15 are arranged on upwardlydirected extension arms 16.

In operation the cleaning of the drop separator takes place in twointervals per hour. During the interval, the six solenoid valves 21located on each side of the separating installation are successivelyopened, so that in a first rinsing process the flat jet nozzles 15 ofthe upper two nozzle pipes 14 activated by the first solenoid valves 21are in operation, in the second interval the flat jet nozzles 15 of thethird nozzle pipe 14 of the upper tier and of the first nozzle pipe 14of the second tier, triggered by the second solenoid valves 21 areoperating, and so on. Each solenoid valve 21 is opened for 2 min., i.e.the duration of one rinsing process is 2 min. and the duration of aninterval is 12 min.

At a precompression of 4 bar, the output of a flat jet nozzle 15 amountsto 30 l/min. For the thirty flat jet nozzles 15 per nozzle pipe 14 theoutput per solenoid valve 21 is 900 l/min. and the total water amountfor both sides in an interval is 7200 l.

During the rinsing process the linear drive moves each middle section 6with a speed of 5 to 15 mm/s, e.g. 9 mm/s, in vertical directionperpendicular to the flow direction of the flue gas, whereby thecleaning jets nozzles move over the blades 5 in the direction indicatedby arrow B and therefore perpendicular to the blades 5, coveringrespectively one half of a blade packet 1. In addition, the cleaningjets are pulsed in the natural frequency of blades 5.

Solid substances with abrasive action, such as sand and/or substances,e.g. sulfuric acid, which chemically dissolve the deposits, can beadmixed.

The number of the required nozzles is reduced by five to ten times andthe water amount required per interval is reduced by two to three timescompared with a cleaning process using stationary, fully conicalcleaning jets.

A drop separator with vertical flow as shown in FIG. 5 is arrangedoptionally downstream of a counter-flow scrubber of flue gas scrubbinginstallation.

The separating installation according to this embodiment has no watercollecting tanks 3.

In addition to the middle sections 6, the frames have two drive sections25 (which can not be seen from FIGS. 5 and 6) on each of the two sidesof the middle sections 6 and parallel thereto. Each drive section 25 isconnected with a driving rod 12. The driving rods 12 traverse a wall ofthe flue gas channel through a packing box 13 and are connected with alinear drive as shown in FIG 1.

The frames are connected with chassis provided with wheels 23 andmountings 24. The wheels for the lower frame are fastened under thedrive sections 25 and the wheels for the upper frame are fastened abovethe drive sections 25. The wheels 23 are on running surfaces,respectively in the case of the upper frame under the running surfaces,of the mountings 24.

In a variant of the drop separator, the frames of the cleaning device,namely the drive profiles 25, are connected over links 10 with theswinging bars 9. The swinging bars 9 are connected over further links 11with carriers in the flue gas channel, or optionally in the case of theupper frame, with the cover of the flue gas channel.

We claim:
 1. A method for cleaning a drop separator, comprising the steps of:(a) mounting a plurality of mutually parallel and spaced apart blades curved in a direction of gas flow over a cross section of a gas channel and extending longitudinally and generally perpendicular to the direction of gas flow, thereby forming deposits on the blades; (b) pulsing cleaning jets of wash water from a plurality of flat jet nozzles across the gas channel over the plurality of blades, thereby spraying the blades with flat cleaning jets removing deposits from the blades; and (c) simultaneously with step (b) displacing the plurality of flat jet nozzles perpendicular to the direction of the gas flow and perpendicular to the longitudinal extent of said blades.
 2. The method defined in claim 1 wherein the wash water is pulsed at a frequency corresponding to the natural frequency of the blades.
 3. The method defined in claim 1, further comprising the step of admixing a substance in the wash water capable of removing said deposits.
 4. The method defined in claim 3, further comprising the step of chemically dissolving the deposits of impurities by the substances.
 5. The method defined in claim 3, further comprising the step of abrading the deposits with the substance.
 6. The method defined in claim 1 wherein the jets of wash water are directed in said direction of gas flow.
 7. The method defined in claim 1 wherein the jets of wash water are directed against the direction of gas flow.
 8. A drop separator comprising:a housing formed with a gas channel in a gas flow which contains material to be removed therefrom;a plurality of spaced apart and mutually parallel blades mounted in the gas channel, each of the blades extending longitudinally perpendicular to a direction of said gas flow and being curved in the direction of gas flow through said gas channel; at least one displaceable frame mounted on the housing in the gas channel; a plurality of flat jet nozzles mounted on the frame and pulsing respective flat jets of wash water over the blades transversely to the direction of gas flow; supply means for delivering the wash water to the plurality of the jet nozzles and including:a supply pipe, and a plurality of flexible hoses connected with the supply pipe and the jet nozzles; and actuating means including at least one linear drive for displacing the frame perpendicular to said direction of gas flow and to the longitudinal extent of said blades.
 9. The drop separator defined in claim 8, further comprising at least one swinging bar operatively connected with the actuating means and pivotally mounted on a cover of said channel to guide said frame in said channel.
 10. The drop separator defined in claim 9 wherein the nozzles are movable angularly to provide an impact angle of the jets within a range from 0° to 15°.
 11. The drop separator defined in claim 8 wherein the supply means further includes:at least one more supply pipe; a plurality of connecting pipes providing communication between the supply pipes; and a plurality of connection sockets in flow communication with connecting pipes and the hoses; and a plurality of valves provided in the sockets.
 12. The drop separator defined in claim 8 wherein said housing has a wall defining said channel and provided with a packing box, said actuating means further including a driving rod extending through the packing box and connected with the linear drive.
 13. The drop separator defined in claim 8 wherein each of said plurality of the flat jet nozzles is provided with a respective mouthpiece formed as a flat funnel.
 14. The drop separator defined in claim 8 wherein each of said nozzles is mounted on a respective arm. 